import java.util.concurrent.Semaphore;

/**
 *  编写代码实现两个线程增加同一个变量
 * 使用 Semaphore 来控制线程安全.
 */
public class Demo1 {
    public static int count = 0;
    public static void main(String[] args) throws InterruptedException {

        // 可用资源为2的信号量.
        Semaphore semaphore = new Semaphore(1);
        // 创建两个线程.
        Thread t1 = new Thread(() -> {
            for (int i = 0; i < 50000; i++) {
                try {
                    semaphore.acquire();
                    count++;
                    semaphore.release();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 50000; i++) {
                try {
                    semaphore.acquire();
                    count++;
                    semaphore.release();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        t1.start();
        t2.start();

        t1.join();
        t2.join();

        System.out.println("count: " + count);
    }
}
